ML19261C077
| ML19261C077 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 03/08/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Mary Johnson SOUTH CAROLINA ELECTRIC & GAS CO. |
| References | |
| NUDOCS 7903140530 | |
| Download: ML19261C077 (1) | |
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- v j MAR 8 1979 In Reply Refer To:
RII:JP0 50-395 South Carolina Electric and Gas Company Attn:
Mr. M. C. Johnson, Vice President and Group Executive - Special Services and Purchasing P. O. Box 764 Columbia, South Carolina 29218 Gent 1emen:
The enclosed Bulletin 79-02 is forwarded to you for action.
A writtet response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, hJ.A. O ames P. O'Reilly D ector t.nclosure IE fiulletin No. 79-02 cc w/ enc 1:
A. A. Smith Quality asurance P. O. Box 8 Jenkinsville, South Carolina 29065 T. L. Conners, Jr.
Conners, Moore and Corbe-1747 Pennsylvania Avenue, N. W.
Washington, D. C.
20006
- 0. S. Bradham, Manager Nuclear Operations P. o. Bo2 8 Jenkinsville, South Carolina 29065 7003140 5 3 o
a UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 March 8, 1979 Cr tsulletin No. 79-@
PIPE SUPPORT BASE PLATE DESIGNS USING CONCRETE EXPANSION ANCHOR BOLTS Description of Circumstances:
While performing inservice inspections during a March-April 1978 refueling outage et Millstone Unit 1, structural failures of pfping supports for safety equipment were observed by the licensee. Subsequent licensee inspections of undamaged supports showed a large percentage of the concrete anchor bolts were not tightened properly.
Deficiency reports, in accordance with 10 CFR 50.55(e), filed by Long Island Lighting Company on Shoreham Unit 1, indicate that design of base plates using rigid plate assumptions has resulted in underestima-tion of loads on some anchor bolts. Initial investigation indicated that nearly fif ty percent of the base plates could not be astomed to behave as rigid plates.
In addition, licensee inspection of ac-he-bolt installations at Shoreham has shown over fif ty percent of the bolt installations to be deficient.
Vendor Inspection Audits by NRC at Architect Engineering firms have shown a wide range of design practices and installation procedures which have been employed for the use of concrete expansion anchors.
The current trends in the industry are toward more rigorous controls and verification of the installation of the bolts.
The data available on dynamic testing of the concrete expansion anchors show fatigue failures can occur at loads substantislly below the bolt static capacities due to material imperfections or notch type stress risers. The data also show low cycle dynamic failures at loads below the bolt static capacities due to joint slippage.
Action to be Taken by Licensees and Permit Holders:
For pipe support base plates that use concrete expansion anchor bolts in Seismic Category I systems as defined by P.egulatory Guide 1.29, " Seismic Design Classification" Revision 1, dated August 1973 or as defined in the applicable FSAR.
1.
Verify that pipe support base plate flexibility was accounted for in the calculation or anchor bolt loads.
In lieu of supporting analysis justifying the assumption of rigidity, the base plates 1 of 3
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